Abstract: To reveal the effects of geographical isolation and human activities on the genetic pattern of Populus euphratica in northwestern China, we analyzed the genetic diversity and population genetic structure of six natural populations (sample size=159) distributed across Qinghai, Gansu, Xinjiang, and Inner Mongolia by using 12 highly polymorphic SSR primers. The results showed that P. euphratica populations maintained a high level of gene-tic diversity (expected heterozygosity=0.62). There were significant genetic differentiations among populations (genetic differentiation index=0.38), forming three relatively independent genetic lineages: the Qinghai lineage, Dunhuang lineage, and mixed lineage. The geographical barriers of the Kunlun Mountains and Qilian Mountains shaped the distinct Qinghai and Dunhuang lineages, respectively, while P. euphratica populations along the ancient Silk Road have formed a mixed lineage spanning large geographical distances due to human-mediated gene flow. The three major lineages identified here should be regarded as independent management units. Our results would provide key genetic evidence for formulating targeted conservation and management strategies for P. euphratica resources.

Key words: Populus euphratica, genetic diversity, genetic structure, geographical isolation, Silk Road, management unit